1. Field of the Invention
The present invention relates to an interactive videotex system for supplying information to users in their homes and, more particularly, to an interactive videotex system with distributed information processing and storage which is hardwired to the user through existing cable television systems.
2. Description of the Related Art
Distributed processing and storage are relatively new concepts in data management and--because of the various technological hurdles--have not been considered until now for application to the field of videotex. The Prodigy.RTM. information service, which is now being marketed nationwide by Sears and IBM, claims to use a distributed database architecture. However, that system only distributes the database to regional mainframe computers. Their underlying technology--as with all other current videotex technology--still relies completely on the maintenance of continuous, real-time, two-way communication of a personal computer (or other terminal) in the home with a mainframe computer at some remote location. Nearly all videotex services use phone lines and modems to link the two, though some experiments with two-way cable TV and other media have been attempted. These existing systems have numerous limitations.
Since each user of a traditional videotex system is directly connected to a central mainframe when on-line, this central computer must be capable of simultaneously handling the many subscribers it gets during prime usage periods, while it may sit almost idle the rest of the time. As the number of users increases, additional large computers must be added to the system at great expense. Any problem with the central computer or the communications net linking it to the users can cause the entire system to cease functioning.
The speed with which information may be retrieved from such systems is limited to the speed with which the central computer can recognize the users' requests and locate the information in its central data storage media. Even the largest and fastest of central computers cannot overcome the severe limitations of how quickly information may be carried by the phone lines or other media that connect it to the user. Phone lines have a narrow bandwidth and can carry only a limited amount of information at any one time. For example, it takes 8 to 10 seconds for a central computer to send a screen full of just text information to a user terminal over a telephone line, assuming a typical communications speed of 2400 baud. A complex graphic or photographic quality image could take at least 1/2 hour per image.
The newer Integrated Services Digital Network (ISDN) and fiber optic cable technologies will provide greater information transmission capability for businesses, but these technologies will not be wired into a large number of individual homes for at least another ten years. Moreover, even using high speed fiber optics connecting a central computer to a home terminal, the largest of computers cannot keep up with an entire city of users especially during prime time. As an example, the largest airline reservation system can only process 8000 transactions per second.
This bandwidth problem has never been adequately addressed by those working in the field because--until very recently--all computer interfaces were just character-based or used very low resolution alphamosaic style displays utilizing protocols such as NAPLPS or Teletel. While simple character-based information may be transmitted over phone lines relatively easily, the resulting display is difficult to interpret and use. Even simple alphamosaic displays take long enough--about 8 seconds--to transmit over a phone line that the level of interactively declines and, with the low quality of the display, the systems tend to become uninteresting and awkard to use. After the novelty wears off, the typical consumer finds that the difficulty of using such systems to obtain useful information, coupled with their slow speed and uninteresting graphics, makes other more traditional ways of obtaining information, i.e., printed information, more attractive.
Graphic user interfaces, particularly those using the high resolution, "photorealistic" displays are far more interesting and easier to use, but require vastly greater amounts of data to be transmitted in order to generate interesting screen images that will respond to the user's requests quickly. What has not been addressed by workers in the videotex field is that, while wide bandwidth transmission media remain very limited and/or expensive, the relative costs of memory media such as magnetic disk drives, dynamic random access chips (DRAMs) and other ways of storing data have been dropping quickly, as has the cost of fast microprocessors that can efficiently access and display data stored in the media. This suggests that a highly distributed architecture would overcome the bandwidth limitations and provide a cost effective and very fast information delivery system. The system of the present invention exploits these ongoing technological changes and thus overcomes the above-noted problems in the videotex field.